This application is the National Stage of International Application No. PCT/GB99/03944, filed Nov. 29, 1999 and published under PCT Article 21(2) in English, and claims priority of United Kingdom Application No. 9828669.3, filed on Dec. 24, 1998. The aforementioned related patent application is herein incorporated by reference.
1. Field of the Invention
This invention relates to an apparatus and method for facilitating the connection of tubulars using a top drive and is, more particularly but not exclusively, intended for facilitating the connection of a section or stand of casing to a string of casing.
2. Description of the Related Art
In the construction of oil or gas wells it is usually necessary to line the borehole with a string of tubulars known as casing. Because of the length of the casing required, sections or stands of say two or three sections of casing are progressively added to the string as it is lowered into the well from a drilling platform. In particular, when it is desired to add a section or stand of casing the string is usually restrained from falling into the well by applying the slips of a spider located in the floor of the drilling platform. The new section or stand of casing is then moved from a rack to the well centre above the spider. The threaded pin of the section or stand of casing to be connected is then located over the threaded box of the casing in the well and the connection is made up by rotation therebetween. An elevator is then connected to the top of the new section or stand and the whole casing string lifted slightly to enable the slips of the spider to be released. The whole casing string is then lowered until the top of the section is adjacent the spider whereupon the slips of the spider are re-applied, the elevator disconnected and the process repeated.
It is common practice to use a power tong to torque the connection up to a predetermined torque in order to make the connection. The power tong is located on the platform, either on rails, or hung from a derrick on a chain. However, it has recently been proposed to use a top drive for making such connection.
Because of the high costs associated with the construction of oil and gas wells time is critical and it has been observed by the applicants that the time to connect a tubular to a top drive using existing equipment could be reduced.
There is described an apparatus for facilitating the connection of tubulars using a top drive in co-pending UK Patent Application No. 98 18358.5, which apparatus comprises a body connectable to a top drive, the body comprising at least one gripping element radially displaceable by hydraulic or pneumatic fluid to drivingly engage the tubular. Preferably, the gripping elements are moveable radially outwardly to engage the inside wall of the tubular.
It has been observed that torques of up to 95,000 Nm (70,000 lbs/ft) are required to make-up a joint.
It has also been observed that the apparatus of the present invention may be used for facilitating rotation of the casing while running the casing down a wellbore.
It has also been observed that a drill bit may be placed on the bottom end of the casing string and used for boring a wellbore. The apparatus of the present invention may be used for facilitating rotation of the casing for boring a wellbore.
According to a first aspect of the invention there is provided an apparatus for facilitating the connection of tubulars using a top drive, the apparatus comprising a supporting member connectable to said top drive characterised in that it further comprises an internal tool for engaging said tubular and an external clamping device for engaging said tubular.
Other features of the first aspect of the present invention are set out in claims 2 to 11.
There is also provided a method for facilitating the connection of tubulars using a top drive, the method comprising the steps of inserting and activating an internal tool for engaging said tubular; rotating said tool and tubular to a low torque, activating an external clamping device for engaging said tubular and rotating said clamping device and said tubular to a high torque.
Preferably, the first torque is sufficient to run a pin on said first tubular into a box and the second torque is sufficient to tighten said connection to its designated value.
According to a second aspect of the invention there is provided an apparatus for facilitating the connection of tubulars, the apparatus comprising a tool for gripping a tubular and at least one piston and cylinder for raising and lowering said tool characterised in that, in use, torque applied to the supporting member is transformed to said tool through said at least one piston and cylinder. Preferably, three piston and cylinders are provided.